The invention relates generally to infant care units such as incubators and infant warmers and relates more particularly to a system, method and apparatus for monitoring the status of an infant being warmed or treated and controlling operation of the incubator or infant warmer.
Infant incubators and infant warmers are used to provide heat support to premature infants who cannot maintain their own body temperature. Temperature control is provided by various different processes. In many incubators and infant warmers the temperature control process is selectable by the user.
Both the control and monitoring of infant warmers and incubators can be provided using various different sensing and control systems. So-called manual mode may be used wherein information is provided as to the temperature in the incubator or the infant space of the infant warmer and the heater output may be set manually. This type of system is an open loop system. Typically some type of alarm is provided to indicate heater power termination if this is not confirmed by the caregiver. Monitoring and control referred to as air control is often used where the user sets the desired air temperature of the incubator or baby warmer space. The system provides for measurement of the actual temperature inside the infant""s compartment or infant space and regulates a heater to supply adequate heat to reach the desired air temperature. An air temperature deviation alarm can be selected by the user, for example between 1.5 and 2.5xc2x0 C. or some similar setting.
Skin control of an infant warmer or incubator is based on a desired skin temperature for the patient and based on a sensing of the actual skin temperature of the patient. A skin temperature sensor is attached to the infant (for example at the abdomen or lower back or head). The incubator or warmer measures the infant""s skin temperature via the skin sensor and regulates a heater to supply adequate heat to reach the desired skin temperature. A skin temperature deviation alarm can be selected for example from 0.3 to 1.0xc2x0 C. An alarm can be triggered if the actual skin temperature falls outside the alarm limits. So called skin control monitoring and control has advantages and is considered a preferred mode of operation for incubators and infant warmers.
U.S. Pat. No. 6,048,304 discloses a process for controlling the operating parameters of an incubator. The process uses skin control concepts and in particular provides multiple sensors such as a first sensor for measuring the infant patients core temperature (such as for measuring the skin temperature at the head or abdomen) and a peripheral skin temperature sensor. Additionally an air temperature sensor measures the actual air temperature in the incubator. The process sets the air temperature in the incubator as a function of both the core temperature and the peripheral temperature of the infant patient. The actual core temperature and peripheral temperature are calculated based on sensed values. The use of both a sensing to determine the core temperature and peripheral temperature is proven to be useful. It has been noted that undercooling can be recognized in the case of highly premature or full-term newborn babies from an intense cooling of the periphery, while the core of the body is still in the normal range. This is based on the body""s attempt to maintain the core temperature by throttling the blood flow to the periphery, thus reducing the heat loss to the environment at the periphery. An increasing fever can be recognized from a decrease in the peripheral temperature with rising core temperature of the body. The body has centralized the blood flow to the core in this case in order to heat to a higher temperature, and it throttles the blood flow to the periphery in order to save heat and to use it to heat the central organs. A subsiding fever can be recognized from the high core temperature of the body with a simultaneously high peripheral temperature. The body uses the large surface of the periphery to cool the core of the body by a corresponding release of heat. The process of U.S. Pat. No. 6,048,304 provides a solution of the problem that temperatures measured at the patient are measured at the skin surface and are therefore distorted by external effects such as air flows. This determination of core and peripheral temperatures based on calculations using sensed values allows operating conditions of the incubator to be set correctly. U.S. Pat. No. 6,048,304 is hereby incorporated by reference.
Recently clinical studies have shown that co-bedding of premature twins in the same warming device can be beneficial to the development of the infants. However, currently available warming devices do not provide the same control methods as discussed above for twins. The problem relates to the fact that two patients are occupying the space. Since one of the twins would have to be selected to be the xe2x80x9csupplierxe2x80x9d of the skin temperature measured via the skin temperature sensor, this could result in a problem since the heat requirements of the two infants could be different. If skin temperature information from only one infant is used, resulting in one infant being comfortable, the other infant could be too warm or too cold.
As such, infant care devices (incubators/warmers) used for co-bedding of premature twins are operated in air or manual mode respectively, thereby avoiding the selection of a xe2x80x9ccontrol infant.xe2x80x9d The user has to manually check both infant temperatures and then adjust the air temperature setting to a value agreeable for both infants. Even if sensors are connected to each of the infants for taking skin temperature readings, hence avoiding the manual taking of temperatures, it is still necessary to operate the device in air/manual mode with the air temperature set and adjusted by the caregiver at regular intervals.
This has the disadvantages of requiring a great deal of time so as to be time intensive for the caregiver. The result may be inconsistent and may depend on the individual caregiver""s attention and thoroughness. Frequent interruptions of the infant""s create xe2x80x9cdown time,xe2x80x9d since the incubator needs to be opened and the infants will be manipulated during the process of taking the temperature of each infant.
The primary object of the invention is to allow the user to operate the incubator in substantially the same manner regardless of the number of infant occupantsxe2x80x94single or double, triple, quadruple, etc. and/or to provide a monitoring and control system and method than monitors and controls based on the patient""s temperature regardless of the number of occupantsxe2x80x94single or double, triple, quadruple, etc.
According to the invention, a system for controlling the heating and temperature monitoring of infant incubators and infant warmers is provided with an incubator or infant warmer space, a heater for heating the space as well as a first temperature sensor and a second temperature sensor. An input device for input of one or more control setting works in conjunction with a control device connected to the heater and to the first temperature sensor and the second temperature sensor. The control device forms a control temperature from an input first skin temperature target control setting for a first patient and an input of a second skin temperature target control setting for a second patient and further patients if present and controls the heater based on a difference between the control temperature and an actual temperature value based on a first actual temperature sensed by the first temperature sensor and a second actual temperature sensed by the second temperature sensor.
The control device preferably calculates the control temperature as the average of the input first skin temperature target for the first patient and the input of the second skin temperature target for a second patient. The actual sensed temperature value may be the average of the first actual temperature sensed by the first temperature sensor and the second actual temperature sensed by the second temperature sensor.
A first input skin temperature deviation limit and a second input skin temperature deviation limit received by the control device may be used by the control device to generate an alarm signal or reject the input first skin temperature target input for the first patient and/or reject the input of the second skin temperature target for the second patient if the control temperature does not overlap both the range of the first input skin temperature deviation limit from the first input skin temperature and the second input skin temperature deviation limit from the second input skin temperature.
A display may be provided for displaying one or more of the first input skin temperature deviation limit, second input skin temperature deviation limit, the first input skin temperature and the second input skin temperature. A graphical interface or other interface using the display may provide the information in one or more of various formats.
The control device may generate an alarm signal when a first actual temperature sensed by the first temperature sensor deviates from the first input skin temperature by more than the first input skin temperature deviation limit or when the second actual temperature sensed by the second temperature sensor deviates from the second input skin temperature by more than the second input skin temperature deviation limit.
According to another aspect of the invention a method is provided for controlling the heating and temperature monitoring of infant incubators and infant warmers, the method including providing an infant space, providing a heater for heating the space, connecting a first temperature sensor to a first patient and placing the patient in the infant space and connecting a second temperature sensor to a second patient and placing the second patient in the infant space. A monitoring and control unit is connected to the first temperature sensor and is connected to the second temperature sensor. An input device is associated with the monitoring and control unit. The input device is used to set a skin temperature target setting for the first patient. The input device is used to set a skin temperature target setting for the second patient. A control temperature is formed from the input first skin temperature target setting and the input second skin temperature target setting. The process heats the space based on a difference between the control temperature and an actual temperature value that is a function of a first actual temperature sensed by the first temperature sensor and a second actual temperature sensed by the second temperature sensor.
According to still another aspect of the invention, an infant heat treatment system is provided with an infant support surface a heating unit a plurality of skin temperature sensors and a monitoring and control unit for controlling the operation of the heating unit to heat the infant on the surface and for receiving input settings including at least a first and second skin temperature setting and allowable deviation settings. The monitoring and control unit is operable in a single patient mode for controlling the heating unit based on a relationship between a temperature signal from at least one of said plurality of skin temperature sensors and at least one skin temperature setting for a single patient on the infant support surface. The monitoring and control unit is also operable in a twin patient mode for controlling the heating unit based on at least a relationship between a temperature signal from a first skin temperature sensor connected to a first infant on the infant support surface and a temperature signal from a second skin temperature sensor connected to a second infant on the infant support surface and a first skin temperature setting based for the first infant and a second skin temperature setting for the second infant where the temperature control setting overlaps a range defined by each of a first skin temperature setting plus or minus a first patient skin temperature deviation setting and defined by a second skin temperature setting plus or minus a second patient skin temperature deviation setting.
In such a twin mode the user can set multiple skin temperatures. In the case of twins two skin temperature targets, Tskin1 set and Tskin2 set, one for each infant, and two skin deviation alarm limits Tda1 and Tda2 (xc2x10.3 to 1.0) are set. The monitoring and control unit algorithm will calculate a control temperature using both skin temperature entries as follows:
Tcontrol=(Tskin1+Tskin2)/2xe2x80x83xe2x80x83(1.0)
As a condition for the algorithm to accept the entries of Tskin1 and Tskin2 the correlation skin deviation alarm limits must have a range with an overlap, which defines the range of the control temperature Tcontrol. This condition may be expressed as follows:
For example Tskin1 less than Tskin2xe2x80x83xe2x80x83(2.0)
Tskin1+Tda1 greater than Tcontrol greater than Tskin2xe2x88x92Tda2xe2x80x83xe2x80x83(2.1)
The control temperature range Txcex94control may then vary but within the range defined by the set skin temperatures Tskin1 set and Tskin2 set and the two skin deviation alarm limits Tda1 and Tda2:
Tskin2xe2x88x92Tda2xe2x89xa6Txcex94controlxe2x89xa6Tskin1+Tda1xe2x80x83xe2x80x83(2.2)
The twin mode differs from skin temperature control based on Tcontrol as described in (1.0) above, being based on skin temperature information from two or more infant patients as opposed to the use of one or more skin temperature settings. This Tcontrol can vary with a temperature range defined by (2.2) without causing any deviation alarm. A deviation alarm will be generated or the setting will be rejected if either Tskin1 set and/or Tskin2 set are outside the control temperature range Txcex94control. The procedure is similar for triplets, quadruplets etc., wherein skin temperature targets, one for each infant, and skin deviation alarm limits are set. The Tcontrol is determined based on the skin temperature information for each of the infants.
Infant care devices which include a lying surface or surface to support the infant and which provide heat to the infant are broadly the concern of the invention. This includes incubators, infant warmers as well as hybrid device which provide both an enclosed incubator space as well as the ability to open up the structure to provide an open infant warmer. The infant care unit may also be a transport incubator, both for in-house and as for use as a complete self-contained mini NICU (with monitoring, ventilator, iv pumps, etc.) used in fixed wing airplanes, helicopters and ambulances. This has similar features to standard incubators/warmers.
The heating device or heating unit may be a single unit or may be multiple units working in concert. The unit may be an air warmer by itself or an air warmer with a humidifier for regulating the moisture content in an incubator or warmer space. In incubators these air warmers typically distribute air at the side edges of the incubator thereby heating the incubator structure itself for better heat transferred to in the infant patient. Additionally the mattress may provide the heat to the infant by contact between the infant and the mattress, thereby providing conductive heat transfer. The air heating unit may include a single heating structure or multiple heating structures and may provide plural outlets as disclosed in U.S. Pat. No. 5,944,651 or directed warm air provided for different purposes. Reference is made to U.S. Pat. No. 5,944,651 which is hereby incorporated by reference. Further the incubator structure may be a multiple walled structure wherein the wall inside is warmer than the outside wall. The heating unit may also include a radiant heating unit for providing heat to the infant patient by radiation. This is typically provided with infant warmers wherein the infant warmer has sidewalls but is open to the top for operation with a radiant heater.
The invention provides a system method and apparatus wherein the caregiver provides an input of at least a skin temperature in single infant mode and skin temperatures for each of two or more infants in twin mode (i.e., for twin infants, triplets, quadruplets, etc.) Additionally at least one deviation alarm temperature limit for the skin temperature of one infant patient is provided for single use mode whereas two skin deviation alarm limits are provided for twin mode use. The invention provides for a formulation of a temperature control based on the two skin temperature settings. The particular actual algorithm used for changing the heat provided by the heating unit may be of various different types as is generally known and as is described herein. Advantageously the control system uses the set parameters in twin mode and deviation limits in a similar manner as in single mode but based on the temperature control formed from the settings of two or more infant patients. Such a control system may be a Proportional Integral Differential (PID) control system. A control of the heating unit for temperature control from U.S. Pat. No. 5,385,529 may be used. U.S. Pat. No. 5,385,529 is hereby incorporated by reference.
Various modes of operation are discussed herein with reference to the invention wherein particularly the invention provides both a twin mode and some other single mode or other single modes. These additional modes can include air mode, skin mode and other modes as mentioned above and also kangaroo mode, a mode wherein the parent of a single child using the infant care device holds the child preferably while the childs temperature is monitored. For Kangaroo mode the setting of the incubator or child warmer is changed to for example air mode such that the childs temperature no longer is used to control the settings of the incubator or child warmer space. Further, the invention provides a twin kangaroo mode wherein one of the twins may be removed from the incubator or child warmer space and may be monitored in kangaroo mode whereas the settings for the incubator itself are switched over to single mode based on the setting for the child still remaining in the incubator and based on the temperature sensed relating to the incubator space and the skin temperature of the child still remaining in the incubator.